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A/C Pressure Zone "A" Diagnosis

WARNING: This page is about a different car, the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, and 2002 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
WARNING: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.
NOTE: For circuit reference, see CONNECTOR IDENTIFICATION  and/or WIRING DIAGRAMS  .
NOTE: Tools Required: ACR 2000 Air Conditioning Service center (J-43600).
NOTE: Definition: The high and low side pressures may be normal or slightly less than normal.
  1. Were you sent here from the A/C PERFORMANCE TEST ? If so, go to next step. If not, go to A/C PERFORMANCE TEST  under PERFORMANCE TESTS.
  2. Refer to the air outlet temperatures recorded during the A/C system performance test. Is there a 2-3 degrees or more difference in the discharge air temperature between the right and left center I/P outlets? If so, go to step  7. If not, go to next step.
  3. Did the customer concern mention that the A/C system output temperatures are good at first, but then turn warm during extended drives? If so, go to next step If not, go to step  5.
  4. Increase engine speed to 2000 RPM. During extended operation of the A/C system, does the low side pressure decrease, possibly accompanied by heavy frost on the liquid line between the orifice tube and the evaporator? If so, see A/C PRESSURE ZONE "D" DIAGNOSIS . If not, go to next step.
  5. Refer to the pressures recorded during the A/C PERFORMANCE TEST  under PERFORMANCE TESTS. Inspect for the following conditions:
    • The high side pressure slightly above the specified pressure ranges but still within zone A. See Figure.
    • The discharge line is hot.
    • The suction line is cool.
    Do the listed conditions exist? If so, go to step  7. If not, go to next step.
  6. Refer to the pressures recorded during the A/C PERFORMANCE TEST . Inspect for the following conditions:
    • The low side pressure slightly lower than the specified pressure ranges but still within zone A. See Figure.
    • The discharge line is warm-to-hot.
    • The suction line is cool-to-warm.
    Do the listed conditions exist? If so, go to next step. If not, go to TEST S: TOO HOT IN VEHICLE  under SYMPTOM TESTS.
  7. The A/C system may be undercharged. Leak test A/C system. See LEAK TESTING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. After system is repaired, recharge the A/C system to specifications. See RECOVERY, EVACUATING & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Go to step  14.
  8. The A/C system may be contaminated. View the ACR 2000 Air Conditioning Service center information screen for detection of foreign gases in the A/C system. If foreign gases exist, go to next step. If not, go to step  10.
  9. Evacuate the A/C system to a scavenging tank. See RECOVERY, EVACUATING & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. After repairs are complete, go to step  14.
  10. The A/C system may contain too much moisture or air. Evacuate and recharge the A/C system to specifications. See RECOVERY, EVACUATING & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. After repairs, operate the A/C system and check the outlet air temperatures. See A/C PERFORMANCE TEST  under PERFORMANCE TESTS. Are the outlet temperatures within the specified ranges? See A/C SYSTEM PERFORMANCE SPECIFICATIONS - WITH FRONT A/C  or A/C SYSTEM PERFORMANCE SPECIFICATIONS - WITH REAR A/C  tables. If so, go to step  15. If not, go to next step.
  11. The A/C system may contain too much refrigerant oil. Recover the refrigerant from the A/C system. See RECOVERY, EVACUATING & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Remove the accumulator. See ACCUMULATOR  under REMOVAL & INSTALLATION. Drain and measure the refrigerant oil from the accumulator. Was there more than 5 oz. (148 ml) of refrigerant oil drained from the accumulator? If so, go to next step. If not, go to step  13.
  12. Reinstall the accumulator. See ACCUMULATOR  under REMOVAL & INSTALLATION. Flush the A/C system. See FLUSHING PROCEDURES in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Add the specified amount of refrigerant oil to the A/C system. See SPECIFICATIONS . Recharge the A/C system. See RECOVERY, EVACUATING & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. After repairs are complete, go to step  14.
  13. Add the specified amount of refrigerant oil to the A/C system. See SPECIFICATIONS . Install the accumulator. See ACCUMULATOR  under REMOVAL & INSTALLATION. Recharge the A/C system. See RECOVERY, EVACUATING & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. After repairs are complete, go to next step.
  14. Record the low and high side pressures and the I/P outlet air temperature. Compare the outlet temperatures to those listed in the A/C System Performance Table. See A/C SYSTEM PERFORMANCE SPECIFICATIONS - WITH FRONT A/C  or A/C SYSTEM PERFORMANCE SPECIFICATIONS - WITH REAR A/C  table. Are the high and low side pressures and outlet temperatures within specifications? If so, go to next step. If not, go to A/C PERFORMANCE TEST .
  15. Operate the system in order to verify the repair. Did you correct the condition? If so, system is okay. If not go to step  2.
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